A spectral-domain OCT study of formerly premature children.

Prat Itharat MDMay 30, 2008

Vanderbilt Eye InstitutePreceptor: Dr. Recchia

Background: Optical coherence tomography (OCT)

OCT analogous to ultrasound imaging

Non-invasive

Uses light waves

Many applications in ophthalmology

Background: OCT

Zeiss Cirrus HD-OCT (Meditec, Dublin, CA)

Acquires 200 linear B-scans

More data points sampled

Faster scanning time Better resolution: up

to 5 microns Less concern for

eccentric fixation and technical skills

Zeiss Stratus OCT

Acquires 6 linear B-scans Fewer data points sampled Slower scanning time Resolution: up to 10 microns More concern for eccentric fixation and technical skills

Zeiss Stratus OCTTime Domain

Zeiss Cirrus HD-OCT Spectral Domain(Meditec, Dublin, CA)

Acquires 6 linear B-scans Acquires 200 linear B-scans

Fewer data points sampled More data points sampled

Slower scanning time Faster scanning time

Resolution: up to 10 microns Better resolution: up to 5 microns

More concern for eccentric fixation and technical skills

Less concern for eccentric fixation and technical skills

Background: SD vs TD OCT

Spectral Domain Time Domain

Courtesy of Zeiss Whitepaper

Background: Prematurity

Background: Prematurity

Escedy et al (2007) noted increase central retinal thickness in formerly premature children

Stratus OCT

Mainly due to presence to ROP

Recchia et al (2007) showed OCT abnormalities in ROP patients - first to suggest that changes may be vestiges of prematurity

Recchia et al (2007) showed OCT abnormalities in ROP patients - first to suggest that changes may be vestiges of prematurity

Recchia et al (2007) showed OCT abnormalities in ROP patients - first to suggest that changes may be vestiges of prematurity

Limitations

Technologically

Methodologically

Hypothesis:

OCT abnormalities are more

common in

formerly premature children than in

full term

children.

OCT and prematurity Study questions:1. Is there a difference in macular

thickness between premature and full-term children?

2. Is there a difference in foveal contour between these groups?

3. Are the OCT findings correlated to the presence of ROP or another variable?

Methods

IRB approval for prospective study

Records of formerly premature infants born prior to 1/1/2001 (treated in the Vanderbilt NICU)

Control group matched for age and refractive error

Methods Group I: premature with ROP (<32 weeks gestational age)

Group II: premature without ROP (<32 weeks gestational age)

Group III: full term (>36 weeks gestational age)

Methods Gestational age, birth weight,

ROP status obtained from records

Cycloplegic refraction

Best corrected visual acuity

Methods Quantitative primary outcome

measures (OCT)-central subfield thickness

-inner (ring) macular thickness

-outer (ring) macular thickness

-total macular volume

Methods Qualitative primary outcome

measures (OCT)

-presence of foveal depression

-preservation of retinal layers

Methods OCT data were reviewed by a trained

physician (FMR) masked to the birth history of the patient

Quality of all scans was assessed and any scans with a signal strength less than 8/10 were discarded

For each eye, a 6 x 6 mm macular cube and 5-line macular raster line scan were interpreted individually

Results: Eyes

Results:

Results: Central subfield thickness

Results: Inner ring retinal thickness

Results: Outer ring retinal thickness

Results: Total macular volume

Results: Foveal contour

Results: Central subfield thickness : inner ring thickness

Results: Gestational age effect?

Discussion:

Significant effect of gestational age

Non-significant effect of ROP

In contrast to prior studies which suggest that ROP is the major determinant of OCT abnormalities

Discussion: Foveal development

Foveal depression occurs by a reduction of inner (ganglion cell and inner nuclear) layers of the retina

Evident by 24-25 weeks of gestation

Continues until four months postnatally

Diagram from Provis et al.

Discussion: Foveal development

Mintz-Hittner et al described smaller foveal avascular zone (FAZ) in formerly premature children

Provis et al showed that the formation of the FAZ (vascular border) precedes foveal depression

These two processes may be interrelated

Discussion: Foveal development

Prematurity may change retinal oxygenation

Disruption of FAZ and foveal formation-Blunted/absent foveal depression-Thickened central macula-Preservation of retinal layers

Interestingly, most of our patients had excellent visual acuity

Limitations Selection bias (less severe ROP, less

severe neurological disease)

Non-matched gestational age

Most ROP staging obtained indirectly through NICU discharge summaries

Inter-rater variability of ROP

Conclusions OCT findings such as increased

central macular thickness and foveal depression blunting may represent hallmarks of prematurity

These findings can be associated with normal visual acuity

Clinical relevance Greater use of OCT in evaluation of

patients with decreased visual acuity

OCT abnormalities may not represent ocular disease

Research studies in which numerical cutoffs are made for inclusion or evaluation of therapeutic response

Acknowledgements

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